function menuMouse(num){
  for (i = 1; i<=6; i++){
    var btnObj = document.getElementById("btn"+i); 
	if(num == btnObj.id.slice(-1)){btnObj.src = "http://image.dicos.com.cn/btn" + num + "b.png"};
    btnObj.onmouseover = function(){
	  this.src = "http://image.dicos.com.cn/btn" + this.id.slice(-1) + "b.png";
	  //this.style.cursor = "pointer";
	};
    btnObj.onmouseout = function(){
	if(num == this.id.slice(-1)){
		return; 
	}else{
		this.src = "http://image.dicos.com.cn/btn" + this.id.slice(-1) + "a.png" 
	}
	}
  }
}